Synaptic vesicle exocytosis is a fundamental process mediating brain function; subsequent synaptic vesicle endocytosis is important to maintain synaptic transmission. Since malfunctions in synaptic vesicle endocytosis have been linked to human diseases, such as Parkinson's disease, epilepsy, and Alzheimer's disease, elucidating the molecular mechanisms for synaptic vesicle endocytosis will have implications not only for understanding neuronal function but also will provide potential targets for developing novel therapies to treat brain diseases. While it is well established that Ca2+ is critical for exocytosi, increasing evidence suggests that Ca2+ may also be important for endocytosis. Although the importance for endocytosis of Ca2+ influx from extracellular space is accepted, the identity of the Ca2+ influx route for endocytosis remains unclear, as Ca2+-permeable channels other than voltage-gated Ca2+ channels may be involved. Transient receptor potential (TRP) channels are a family of non-selective cation channels with high expression levels in the brain. TRP melastatin 7 (TRPM7), a member of the TRP superfamily, is a Ca2+- permeable channel. We hypothesize that the Ca2+-permeable TRPM7, located on endocytic vesicles, acts as the Ca2+ influx route to regulate endocytosis. Our hypothesis is well supported by the preliminary data described in this proposal. We will test this hypothesis using biophysical and live-cell imaging assays in chromaffin cells and neurons to measure the outcome of molecular biological manipulations such as transgenetic TRPM7 knockout animal models and shRNA-mediated gene knockdown.